1. Technical Field
The present invention concerns a method of depositing layers on a plurality of semiconductor substrates simultaneously and a reactor arrangement for layer deposition on a plurality of substrates.
2. Discussion of Related Art
The development of silicon-germanium-carbon technology has made it possible to manufacture semiconductor devices which contain functional layers with a hitherto unattainable combination of a particularly small layer thickness and a high level of dopant concentration. In that way it was possible for the economically highly developed silicon technology also to be used for devices which are suitable for high frequency, and in part replace the hitherto dominant technology based on III-V semiconductors such as gallium arsenide.
Si/SiGe—C technology profits on the one hand from the advantageous electronic properties of Si/SiGe heterostructures over pure Si structures and on the other hand from the dual effect of the incorporation of carbon. Carbon can compensate for lattice dislocation adaptation of SiGe in relation to Si and in addition represses the diffusion of dopants, which as a consequence leads to unwanted layer spread in transistor structures.
The advantages of Si/SiGe—C technology however could come to fruition only on the basis of the accompanying development of new deposition methods which are adapted to the particular demands of the new semiconductor structures. Thus low-temperature deposition methods were developed, which as far as possible avoid diffusion-promoting process steps at high temperatures.
WO 03/012840 A2 discloses such a low-temperature method of manufacturing thin epitaxial layers. In those methods a plurality of substrates are initially subjected to external preliminary cleaning and then subjected to a hydrogen treatment at a high temperature of between 750 and 1100° C. (“hydrogen prebake”). After that preliminary treatment the substrates are coated in a low-pressure hot or warm wall batch reactor at temperatures which are lower in comparison with the hydrogen treatment.
It is further known from WO 03/012840 A2 for the hydrogen prebake operation to be carried out in a first reactor chamber and for the layer deposition operation to be carried out in a second reactor chamber. After the hydrogen prebake step the substrates are transferred from the first reactor chamber into the second. Transport is effected through a transport chamber in an inert atmosphere or vacuum.
U.S. Pat. No. 6,488,778 B1 discloses a similar arrangement. A problem with the method described in those documents is transport between the reactor chambers after the hydrogen treatment. Due to the change in the gas atmosphere at elevated substrate temperatures, unwanted reactions can occur and fresh impurities can come about on the surface of the substrates which have just been cleaned, and they can adversely affect the homogeneity of the subsequent layer deposition operation. In addition handling of the wafers for transport from the first reactor chamber into the second chamber is complicated and time-consuming.
Therefore the technical object of the invention is to provide a method of and an apparatus for layer deposition, in which the above-specified disadvantages do not occur.